A known automatic assembling apparatus which has been put to use in an assembly line for the body structures of automotive vehicles largely comprises a work tansfer mechanism for moving an incomplete assembly of a vehicle body structure into a position in which additional component members of the body structure are to be assembled to the incomplete assembly, and a set of assembling fixtures for moving the additional component members into positions suitable for being mounted on the incomplete assembly which is clamped in position. After the incomplete assembly of the vehicle body structure and the additional component members are thus held in predetermined positions with respect to each other, welding robots are put into operation to weld the additional component members to the incomplete assembly for thereby completing the vehicle body structure.
An automatic assembling apparatus of this nature is capable of assembling body structures of different types of vehicles such as vehicles of the sedan type and vehicles of the hardtop type, provided the two types of vehicles are of the same model. The assembling apparatus is, however, unable to handle body structures of different models and, for this reason, it has been required to set up two independent assembly lines for the assemblage of vehicle body structures of the two different models. This requires a disproportionately large amount of investment for the installation of the dual production lines and imposes a useless burden on automobile manufacturers especially when vehicles produced by the manufacturers are to be remodelled. If it is desired to re-use the assembly line for vehicles of the prior model, not a small number of fittings and fixtures in the assembly line must be discarded as useless, decreasing the feasibility of the existing assembly line. When, furthermore, the assembling fixtures are to be totally exchanged with new ones, large amount of time and labor are required for the disconnection and reconnection of the pipings and wirings during exchange of the fixtures.
The present invention is based on a discovery that works of two different models can be assembled in a single assembly line if two sets of fixtures are mounted respectively on the opposite sides of a rotatable base structure so as to permit selective use of the two sets of fixtures depending upon the models of the works to be completed. By adoption of such an arrangement, works of two different models can be assembled in a single line so that not only the cost for the production equipment can be reduced but the problems which have been concomitant with conventional assembling lines can be drastically solved.
When the rotatable base structure is to be turned to exchange the assembling fixtures to be put to use, the wirings leading from sources of power and control signals for the assembling apparatus must be disconnected from the fixtures to be put out of use and connected to the fixtures to be put to use. A rotary-type electric connector assembly is useful for permitting selective connection of the wirings to the two sets of fixtures. A conventional rotary-tye connector assembly comprising a combination of two fixed and rotatable contact blocks may be arranged in such a manner that the rotatable contact block is rotatable with the base structure of the assembling apparatus and the fixed contact block is fixed to, for example, the frame structure of the assembling apparatus. When the base structure is turned to exchange the assembling fixtures to be put to use, the rotatable contact block is also turned with respect to the fixed contact block so that the contact elements carried on the fixed contact block are disconnected from one set of contact elements on the rotatable contact block and are connected to another set of contact elements on the rotatable contact block.
The two contact blocks in an ordinary rotary-type connector assembly are held in face-to-face contact with each other so that the rotatable contact block is caused to slide on the fixed contact block when the former is turned with respect to the latter. In the arrangement of this nature, the contact elements on one of the contact blocks slide on the other contact block and the contact elements carried thereon so that the contact blocks and the contact elements carried thereon tend to wear early. Such a tendency is pronounced especially in a connector assembly utilized in an automatic assembling apparatus for vehicle body structures because as many as 100 contact elements are included in the connector assembly. A conventional rotary-type connector assembly is, for this reason, not fit for use for a prolonged period of time when used in an automatic assembling apparatus for vehicle body structure.
Another drawback of a prior-art rotary-type connector assembly is that the cables leading from the rotatable contact block are caused to twist when the contact block is turned with respect to the fixed contact block. This may cause breaks of the cables during use of the connector assembly. To avoid such a difficulty, it will be required to constitute the cables by strongly built cables such as those using music wires and/or to arrange the cables in loose conditions so as to be capable of taking up the rotation of the cables. These expedients not only give rise to an increase in the cost for the installation of the production equipment but can not perfectly eliminate the possibility that the cables may be broken by twisting action. If the cables happen to break during assembling operation, it is required to shut down the assembly line as a whole, causing reduction in the production efficiency.